Effect of rosiglitazone on HDL metabolism in subjects with metabolic syndrome and low HDL

Environmental Factors Modifying HDL Functionality

BACKGROUND

Currently, it has been recognized that High-Density Lipoproteins (HDL) functionality plays a much more essential role in protection from atherosclerosis than circulating HDL-cholesterol (HDL-C) levels per se. Cholesterol efflux from macrophages to HDL, cholesterol efflux capacity (CEC) has been shown to be a key metric of HDL functionality. Thus, quantitative assessment of CEC may be an important tool for the evaluation of HDL functionality, as improvement of HDL function may lead to a reduction of the risk for Cardiovascular disease (CVD).

INTRODUCTION

Although the cardioprotective action of HDLs is exerted mainly through their involvement in the reverse cholesterol transport (RCT) pathway, HDLs also have important anti-inflammatory, antioxidant, antiaggregatory and anticoagulant properties that contribute to their favorable cardiovascular effects. Certain genetic, pathophysiologic, disease states and environmental conditions may influence the cardioprotective effects of HDL either by inducing modifications in lipidome and/or protein composition or in the enzymes responsible for HDL metabolism. On the other hand, certain healthy habits or pharmacologic interventions may actually favorably affect HDL functionality.

METHOD

The present review discusses the effects of environmental factors, including obesity, smoking, alcohol consumption, dietary habits, various pharmacologic interventions, as well as aerobic exercise, on HDL functionality.

RESULT

Experimental and clinical studies or pharmacological interventions support the impact of these environmental factors in the modification of HDL functionality, although the mechanisms that are mediated are poorly understood.

CONCLUSION

Further research should be conducted to unreal the underlying mechanisms of these environmental factors and to identify new pharmacologic interventions, capable of enhancing CEC, improving HDL functionality and potentially improving cardiovascular risk.

Insulin sensitization causes accelerated sinus nodal dysfunction through autophagic dysregulation in hypertensive mice

Insulin sensitizers, while effective in glucose-lowering for diabetes control, are linked to an increased risk of heart disease through mechanisms that are not well understood. In this study, we investigated the molecular mechanisms underlying the effects of insulin sensitization on cardiac sinus node dysfunction. We used pharmacologic or genetic approaches to enhance insulin sensitivity, by treating with pioglitazone or rosiglitazone, or through phosphatase and tensin homolog (PTEN) deletion in cardiomyocytes respectively. We employed an angiotensin II (Ang II)-induced hypertensive animal model which causes sinus node dysfunction and accumulation of oxidized calcium/calmodulin-dependent protein kinase II (CaMKII), which also serves as a biomarker for this defect. While neither PTEN deficiency nor insulin sensitizers caused sinus node dysfunction in normotensive mice, both accelerated the onset of sinus node dysfunction and CaMKII oxidation in hypertensive mice. These abnormalities were accompanied by a significant defect in autophagy as revealed by unc-51 like autophagy activating kinase 1 (ULK1) signaling. Indeed, mice deficient in ulk1 in cardiomyocytes and the sinus node also showed early onset of slow atrial impulse conduction with frequent sinus pauses and upregulated CaMKII oxidation following Ang II infusion similar to that seen with PTEN deficiency, or treatment with insulin sensitizers. To further elucidate the role of autophagy in sinus node dysfunction, we treated mice with a peptide D-Tat-beclin1 that enhanced autophagy, which significantly abrogated the frequent sinus pauses and accumulation of oxidized CaMKII induced by insulin sensitizers treatment, or PTEN deficiency in hypertensive animals. Together, these findings provide clear evidence of the detrimental cardiac effects of insulin sensitization that occurs through failure of autophagy-mediated proteolytic clearance.

Human geroprotector discovery by targeting the converging subnetworks of aging and age-related diseases

A key goal of geroscience research is to identify effective interventions to extend human healthspan, the years of healthy life. Currently, majority of the geroprotectors are found by screening compounds in model organisms; whether they will be effective in humans is largely unknown. Here we present a new strategy called ANDRU (aging network based drug discovery) to help the discovery of human geroprotectors. It first identifies human aging subnetworks that putatively function at the interface between aging and age-related diseases; it then screens for pharmacological interventions that may "reverse" the age-associated transcriptional changes occurred in these subnetworks. We applied ANDRU to human adipose gene expression data from the Genotype Tissue Expression (GTEx) project. For the top 31 identified compounds, 19 of them showed at least some evidence supporting their function in improving metabolic traits or lifespan, which include type 2 diabetes drugs such as pioglitazone. As the query aging genes were refined to the ones with more intimate links to diseases, ANDRU identified more meaningful drug hits than the general approach without considering the underlying network structures. In summary, ANDRU represents a promising human data-driven strategy that may speed up the discovery of interventions to extend human healthspan.

Thiazolidinediones as antidiabetic agents: A critical review

Thiazolidinediones (TZDs) or Glitazones are an important class of insulin sensitizers used in the treatment of Type 2 diabetes mellitus (T2DM). TZDs were reported for their antidiabetic effect through antihyperglycemic, hypoglycemic and hypolipidemic agents. In time, these drugs were known to act by increasing the transactivation activity of Peroxisome Proliferators Activated Receptors (PPARs). The clinically used TZDs that suffered from several serious side effects and hence withdrawn/updated later, were full agonists of PPAR-γ and potent insulin sensitizers. These drugs were developed at a time when limited data were available on the structure and mechanism of PPARs. In recent years, however, PPAR-α/γ, PPAR-α/δ and PPAR-δ/γ dual agonists, PPAR pan agonists, selective PPAR-γ modulators and partial agonists have been investigated. In addition to these, several non PPAR protein alternatives of TZDs such as FFAR1 agonism, GPR40 agonism and ALR2, PTP1B and α-glucosidase inhibition have been investigated to address the problems associated with the TZDs. Using these rationalized approaches, several investigations have been carried out in recent years to develop newer TZDs devoid of side effects. This report critically reviews TZDs, their history, chemistry, mechanism mediated through PPAR, recent advances and future prospects.

Current and future therapies for addressing the effects of inflammation on HDL cholesterol metabolism

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide. Inflammatory processes arising from metabolic abnormalities are known to precipitate the development of CVD. Several metabolic and inflammatory markers have been proposed for predicting the progression of CVD, including high density lipoprotein cholesterol (HDL-C). For ~50 years, HDL-C has been considered as the atheroprotective 'good' cholesterol because of its strong inverse association with the progression of CVD. Thus, interventions to increase the concentration of HDL-C have been successfully tested in animals; however, clinical trials were unable to confirm the cardiovascular benefits of pharmaceutical interventions aimed at increasing HDL-C levels. Based on these data, the significance of HDL-C in the prevention of CVD has been called into question. Fundamental in vitro and animal studies suggest that HDL-C functionality, rather than HDL-C concentration, is important for the CVD-preventive qualities of HDL-C. Our current review of the literature positively demonstrates the negative impact of systemic and tissue (i.e. adipose tissue) inflammation in the healthy metabolism and function of HDL-C. Our survey indicates that HDL-C may be a good marker of adipose tissue health, independently of its atheroprotective associations. We summarize the current findings on the use of anti-inflammatory drugs to either prevent HDL-C clearance or improve the function and production of HDL-C particles. It is evident that the therapeutic agents currently available may not provide the optimal strategy for altering HDL-C metabolism and function, and thus, further research is required to supplement this mechanistic approach for preventing the progression of CVD.

LINKED ARTICLES

This article is part of a themed section on Targeting Inflammation to Reduce Cardiovascular Disease Risk. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.22/issuetoc and http://onlinelibrary.wiley.com/doi/10.1111/bcp.v82.4/issuetoc.

Cardiovascular disease risk reduction by raising HDL cholesterol--current therapies and future opportunities

Since the first discovery of an inverse correlation between high-density lipoprotein-cholesterol (HDL-C) levels and coronary heart disease in the 1950s the life cycle of HDL, its role in atherosclerosis and the therapeutic modification of HDL-C levels have been major research topics. The Framingham study and others that followed could show that HDL-C is an independent cardiovascular risk factor and that the increase of HDL-C of only 10 mg·L(-1) leads to a risk reduction of 2-3%. While statin therapy and therefore low-density lipoprotein-cholesterol (LDL-C) reduction could lower coronary heart disease considerably; cardiovascular morbidity and mortality still occur in a significant portion of subjects already receiving therapy. Therefore, new strategies and therapies are needed to further reduce the risk. Raising HDL-C was thought to achieve this goal. However, established drug therapies resulting in substantial HDL-C increase are scarce and their effect is controversial. Furthermore, it is becoming increasingly evident that HDL particle functionality is at least as important as HDL-C levels since HDL particles not only promote reverse cholesterol transport from the periphery (mainly macrophages) to the liver but also exert pleiotropic effects on inflammation, haemostasis and apoptosis. This review deals with the biology of HDL particles, the established and future therapeutic options to increase HDL-C and discusses the results and conclusions of the most important studies published in the last years. Finally, an outlook on future diagnostic tools and therapeutic opportunities regarding coronary artery disease is given.